6,11-substituted-6,11-dihydrobenzo[b]quinolizinium salts and compositions and method of use thereof

ABSTRACT

6,11-Substituted-6,11-dihydrobenzo[b]quinolizinium salts, pharmaceutical compositions containing them and methods for the treatment or prevention of neurodegenerative disorders or neurotoxic injuries utilizing them.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of our application Ser. No.08/121,626, filed Sep. 14, 1993, now abandoned.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The invention relates to6,11-substituted-6,11-dihydrobenzo[b]quinolizinium salts, tocompositions containing the same and to the method of use thereof in thetreatment or prevention of neurodegenerative disorders or neurotoxicinjuries.

(b) Information Disclosure Statement

Fields, U.S. Pat. No. 3,517,073 issued Jun. 23, 1970, disclosescompounds of the formula: ##STR1## wherein each of R¹, R², R³ and R⁴when taken separately, is hydrogen, lower alkyl, lower aryl, loweracyloxy, lower alkoxy, nitro, halogen, lower acylamino, di(lower alkyl)amino; one group of R¹ and R², R² and R³, and R³ and R⁴, preferably R¹and R², and R³ and R⁴, each group when taken together, represents afused ring system containing up to three 6-member carbocyclic andnitrogen-containing heterocyclic rings at least one of which is anaromatic ring, and having no more than two nuclear nitrogens in anyring, which may be unsubstituted or substituted with one or more of thesubstituents defined by R¹, R², R³ and R⁴ ; each of R⁵ and R⁶, whentaken separately is hydrogen, lower alkyl or lower aryl; each of R⁷ andR⁸, when taken separately, is hydrogen; R⁷ and R⁸, when taken together,represent a fused ring system as defined hereinbefore; R⁹, when takenindividually, is methylene or lower alkyl, lower aryl, lower alkenyl,halogen, or cyano substituted methylene; R¹⁰, when taken individually,is a protected carbonyl group; R⁹ and R¹⁰, when taken together,represent a fused aromatic carbocyclic or heterocyclic ring system,whose valence bonds are from adjacent carbons, containing up to three6-membered carbocyclic and nitrogen-containing heterocyclic rings havingno more than two nitrogens in any ring and which may be substituted withone or more of the substituents defined by R¹, R², R³ and R⁴. Among thecompounds specifically disclosed are12,12-diethoxy-11-methyl-9,10-ethano-9,10-dihydro-4a-azoniaanthraceneperchlorate and9,10-(O-benzeno)-9,10-dihydro-5-methyl-4a-azoniaanthracene perchlorate.Also disclosed are compounds of the formula: ##STR2## wherein R¹ -R¹⁰are as defined above and m is an odd integer having a value of from 1 to5, inclusive. Among the compounds specifically disclosed are12,12-diethoxy-11-methyl-9,10-ethano-4a-aza-1,2,3,4,4a,9,9a,10-octahydroanthraceneperchlorate acid salt,9,10-(O-benzeno)-5-methyl-4a-aza-1,2,3,4,4a,9,9a,10-octahydroanthraceneand12,12-diethoxy-9,10-ethano-11-bromo-4a-aza-1,2,3,-4,4a,9,9a,10-octahydroanthracene.The above-described compounds are disclosed as being intermediates inthe synthesis of 2-napthol derivatives and various anthracenederivatives.

Fields et al., J. Org. Chem. 1968, 33(1), 390-395, disclose a series ofsixteen Diels-Alder adducts prepared from a 4a-azoniaanthracene ion andvarious dienophiles. Among the compounds specifically disclosed are12-ethyl,12-hydroxymethyl and12-ethylene-9,10-dihydro-4a-azonia-9,10-ethanoanthracene bromides;12-phenyl-12-(4-morpholinyl), 12-methyl-12-(1-methylethylene),12,12-diethoxy-11-bromo and12-diethylamino-11-phenyl-9,10-dihydro-4a-azonia-9,10-ethanoanthraceneperchlorates, as well as 9,10[1',2']cyclopentyl and9,10[2',3']tetrahydropyranyl-9,10-dihydro-4a-azoniaanthraceneperchlorates. No utility is disclosed for these compounds.

Fields and Regan, J. Org. Chem. 1971, 36(20), 2986-2990, disclosecompounds of the formula: ##STR3## wherein R is H, Br, or OAc, asintermediates in the synthesis of substituted8-tert-butyl-1-(2-pyridyl)napthalenes.

Fields and Regan, J. Org. Chem. 1971, 36(20), 2991-2994, disclosecompounds of the formula: ##STR4## wherein R is H, CH₃, C₆ H₅, or Br, asintermediates in the synthesis of 2-pyridylnapthols.

Fields, J. Org. Chem. 1971, 36(20), 3002-3005, discloses a series ofsubstituted 12,12-diethoxy-9,10-ethano-9,10-dihydro-4a-azoniaanthracenesand the corresponding derivatives wherein the pyridinium moiety ispartially or completely reduced, as intermediates in the synthesis ofsubstituted 2-napthols. Among the compounds specifically disclosed is12,12-diethoxy-5,11-dimethyl-9,10-ethano-9,10-dihydro-4a-azoniaanthraceneperchlorate. Also disclosed is a series of substituted9,10-(O-benzeno)-9,10-dihydro-4a-azoniaanthracenes and the correspondingderivatives wherein the pyridinium moiety is partially or completelyreduced, as intermediates in the synthesis of substituted anthracenes.Among the compounds specifically disclosed is9,10-(O-benzeno)-9,10-dihydro-4a-azoniaanthracene perchlorate.

Westerman and Bradsher, J. Org. Chem. 1971, 36(7), 969-970, disclosecompounds of the formula: ##STR5## wherein R is CH₃, CH(CH₃)₂, H, F, I,Cl, Br, CO₂ H, CO₂ CH₃, or NO₂. No utility is disclosed for thesecompounds.

Bradsher and Day, J. Het. Chem. 1973, 10, 1031-1033, disclose fourDiels-Alder adducts prepared from acridizinium perchlorate andcyclopentadiene, methyl vinyl ether, norbornadiene and maleic anhydride.No utility is disclosed for these compounds.

Fields and Regan, J. Org. Chem. 1970, 35(6), 1870-1875, disclosecompounds of the formula: ##STR6## wherein R is H, CH₃ or C₆ H₅. Alsospecifically disclosed are9,10-dihydro-12,12-dimethoxy-11,11-dimethyl-4a-azonia-9,10-ethanoanthraceneperchlorate and9,10-dihydro-9,11-dimethyl-12,12-diethoxy-4a-azonia-9,10-ethanoanthraceneperchlorate. The compounds are said to be intermediates in the synthesisof 9,10-dihydro-12-oxo-4a-azonia-9,10-ethanoanthracenes.

Fields et al., J. Org. Chem. 1971, 36(20), 2995-3001, disclose9,10-dihydro-4a-azonia-9,10-O-benzenoanthracene perchlorate and severalanalogs as intermediates in the synthesis of various9-(2-pyridyl)anthracenes.

Fields and Miller, J. Het. Chem. 1970, 7, 91-97, disclose a compound ofthe formula: ##STR7## as an intermediate in the synthesis of thecorresponding 5,8-dione salt.

Bradsher and Stone, J. Org. Chem. 1968, 33(2), 519-523, disclose aseries of Diels-Alder adducts prepared from an acridizinium ion andmaleic anhydride, maleate esters, fumarate esters and variouspara-substituted styrenes in which the para substituent is H, CH₃, OCH₃or NO₂. No utility is disclosed for these compounds. A substantiallysimilar disclosure for the preparation of Diels-Alder adducts fromacridizinium bromide and maleic anhydride, maleate or fumarate esterscan be found in Bradsher and Solomons, J. Am. Chem. Soc. 1958, 80,933-934.

Bradsher and Stone, J. Org. Chem. 1969, 34(6), 1700-1702, disclosecompounds of the formula: ##STR8## wherein R is H, or CH₃ ; R' is H, orCH₃ ; R" is OCH₃, CH₃, H, or NO₂ ; and X⁻ is perchlorate; without anindication of utility. Also disclosed are the Diels-Alder adductsobtained from acridizinium perchlorate and diethyl maleate, diethylfumarate or dimethyl maleate, without an indication of utility.

Burnham and Bradsher, J. Org. Chem. 1972, 37(3), 355-358, disclosecompounds of the formula: ##STR9## wherein R¹ is Ph, and R² is OEt; orR¹ is H, and R² is OEt, OBu, OAc, N-carbazolyl or 1-pyrrolidin-2-one,without an indication of utility

Parham et al., J. Org. Chem. 1972, 37(3), 358-362, disclose compounds ofthe formula: ##STR10## wherein R is H₂, (CH₂)₃, C(O)NHC(O),C(O)N(CH₃)C(O), C(O)OC(O), CH₂ OCH₂, or CH₂ NH₂ ⁺ CH₂, without anindication of utility.

Bradsher et al., J. Am. Chem. Soc. 1977, 99(8), 2588-2591, disclosecompounds of the formula: ##STR11## wherein: R¹ ═R² ═R⁴ ═R⁵ ═H; R¹ ═Me,and R² ═R⁴ ═R⁵ ═H; R¹ ═R⁴ ═R⁵ ═H, and R² ═Me; and R¹ ═H, and R² ═R⁴ ═R⁵═Me. No utility is disclosed for these compounds.

Bradsher et al., J. Org. Chem. 1978, 43(5), 822-827, disclose compoundsof the formula: ##STR12## wherein: R¹ is OEt and R is Me, H, F, Cl, CO₂Me or NO₂ ; R¹ is O--Ph--p--X, wherein X is CH₃, OCH₃, H, C(O)CH₃, orNO₂, and R is hydrogen; and R¹ is N-carbazolyl and R is hydrogen. Noutility is disclosed for these compounds.

Westerman and Bradsher, J. Org. Chem. 1978, 43(15), 3002-3006, disclosea series of Diels-Alder adducts prepared from an acridizinium ion andvarious unsymmetrical alkenes, without an indication of utility. Amongthe compounds specifically disclosed are6,11[2',3']indanyl-6,11-dihydroacridizinium tetrafluoroborate, and12-phenyl-13-(2-pyridyl)-6,11-dihydro-6,11-ethanoacridiziniumtetrafluoroborate.

Westerman and Bradsher, J. Org. Chem. 1979, 44(5), 727-733, disclose aseries of Diels-Alder adducts prepared from a substituted orunsubstituted acridizinium cation and various polarizable alkeneswithout an indication of utility. Among the compounds specificallydisclosed are 12,12-diphenyl-6,11-dihydro-6,11-ethanoacridiziniumperchlorate or bromide,9-methyl-6,11[2',3']indanyl-6,11-dihydroacridizinium tetrafluoroborate,and 7,10-dimethyl-12-phenyl-12-(4-morpholinyl),9-methyl-12-phenyl-12-(4-morpholinyl), 12-(2-pyridyl), and9-methyl-12-(2-pyridyl)-6,11-dihydro-6,11-ethanoacridiziniumtetrafluoroborates.

Bradsher et al., J. Org. Chem. 1979, 44(8), 1199-1201, disclose a seriesof Diels-Alder adducts prepared from a substituted or unsubstitutedacridizinium ion and cyclopropene or 1-methylcyclopropene, without anindication of utility.

Hart et al., Tetrahedron Letters 1975, 52, 4639-4642, disclose acompound of the formula: ##STR13## as an intermediate in the synthesisof 1,4,5,8,9-pentamethylanthracene.

SUMMARY OF THE INVENTION

The invention relates to compounds of the Formula I: ##STR14## wherein:R¹ is hydrogen, or lower-alkyl;

R² is hydrogen, or from one to four, the same or different, halogensubstituents in any of the 7-,8-,9- or 10-positions;

A is cycloalkenyl, or said ring substituted at any available carbon atomthereof by lower-alkylidene; and

X⁻ is an anion; or a hydrate thereof; or a stereoisomer thereof; withthe proviso that when R¹ and R² are hydrogen and X⁻ is Br⁻, or ClO₄ ⁻, Acannot be [3',4']cyclopentenyl.

The compounds of Formula I bind to the PCP receptor and are thus usefulin the treatment or prevention of neurodegenerative disorders orneurotoxic injuries.

Preferred compounds of Formula I above are those wherein:

R¹ is hydrogen, or methyl;

R² is hydrogen or a bromide or fluorine substituent in any of the7-,8-,9- or 10-positions;

A is cyclopentenyl, or cyclohexenyl ring, or said cyclopentenyl ringsubstituted on any available carbon atom thereof by lower-alkylidene;and

X⁻ is an anion;

Particularly preferred compounds of Formula I above are those wherein:

R¹ is hydrogen, or methyl;

R² is hydrogen or 9-Br or 9-F;

A is a [3',4']cyclohexenyl, [3',4']cyclopentenyl, or[5'-isopropylidene-[3',4']cyclopentenyl] ring; and

X⁻ is an anion.

The invention further relates to pharmaceutical compositions whichcomprise a compound of Formula I: ##STR15## wherein: R¹ is hydrogen, orlower-alkyl;

R² is hydrogen, or from one to four, the same or different, substituentsin any of the 7-,8-,9- or 10-positions selected from the groupconsisting of halogen, nitro, lower-alkoxy, hydroxy, and lower-alkyl;

A is a member selected from the group consisting of cycloalkenyl,tetrahydrofuranyl, cycloalkyl, cycloalkenyl substituted at any availablecarbon atom thereof by lower-alkylidene; and phenyl; and

X⁻ is an anion;

or a hydrate thereof; or a stereoisomer thereof; together with apharmaceutically acceptable carrier, adjuvant, diluent, or vehicle; withthe following provisos a) when R¹ is hydrogen, R² is 9-nitro and X⁻ isClO₄ ⁻, A cannot be [3',4']cyclopentenyl; b) when R¹ is hydrogen, R² is7,10-dihydroxy and X⁻ is Br⁻, A cannot be [3',4']cyclopentenyl; (c) whenR¹ and R² are hydrogen and X⁻ is ClO₄ ⁻, A cannot be phenyl; and (d)when R¹ is hydrogen, R² is 9-methyl and X⁻ is ClO₄ ⁻, A cannot bephenyl.

The invention further relates to a method for the treatment orprevention of neurodegenerative disorders or neurotoxic injuries whichcomprises administering to a patient in need of such treatment aneffective amount of a compound of the formula: ##STR16## wherein: R¹ ishydrogen, or lower-alkyl;

R² is hydrogen, or from one to four, the same or different, substituentsin any of the 7-,8-,9- or 10-positions selected from the groupconsisting of halogen, nitro, lower-alkoxy, hydroxy, and lower-alkyl;

A is a member selected from the group consisting of cycloalkenyl,tetrahydrofuranyl, cycloalkyl, cycloalkenyl substituted at any availablecarbon atom thereof by lower-alkylidene; and phenyl; and

X⁻ is an anion;

or a hydrate thereof; or a stereoisomer thereof; with the followingprovisos a) when R¹ is hydrogen, R² is 9-nitro and X⁻ is ClO₄ ⁻, Acannot be [3',4']cyclopentenyl; b) when R¹ is hydrogen, R² is7,10-dihydroxy and X⁻ is Br⁻, A cannot be [3',4']cyclopentenyl; (c) whenR¹ and R² are hydrogen and X⁻ is ClO₄ ⁻, A cannot be phenyl; and (d)when R¹ is hydrogen, R² is 9-methyl and X⁻ is ClO₄ ⁻, A cannot bephenyl.

DETAILED DESCRIPTION INCLUSIVE OF PREFERRED EMBODIMENTS

The term lower-alkyl as used herein means linear or branched hydrocarbonchains having one to about four carbon and thus includes methyl, ethyl,isopropyl, n-butyl, sec-butyl, and the like.

The term halogen as used herein means bromine, chlorine, iodine, andfluorine.

The term lower-alkoxy as used herein means linear or branched alkyloxysubstituents having one to about four carbon atoms and thus includesmethoxy, ethoxy, propoxy, isopropoxy, butoxy, sec-butoxy, and the like.

The term cycloalkenyl as used herein means C₅ through C₇ unsaturatedmonocyclic hydrocarbon residues and thus includes cyclopentenyl,cyclohexenyl and cycloheptenyl.

The term cycloalkyl as used herein means C₅ through C₇ unsaturatedmonocyclic hydrocarbon residues and thus includes cyclopentyl,cyclohexyl and cycloheptyl.

The term lower-alkylidene as used herein means linear or branchedhydrocarbon chains having one to about four carbon atoms and thusincludes methylidene, ethylidene, propylidene, isopropylidene,sec-butylidene and the like.

The term anion (X⁻) as used herein means the anion of an organic acid(includes anions of organic monoacids, as well as monoanions of organicdiacids) which is at least as strong as acetic acid, and thus includesanions of such acids as acetic acid, methanesulfonic acid,toluenesulfonic acid, trifluoromethanesulfonic acid,(-)-dibenzoyl-L-tartaric acid [(-)-DBT], (+)dibenzoyl-D-tartaric acid[(+)-DBT], and the like; or it means an inorganic acid anion such aschloride, bromide, perchlorate, PF₆ ⁻ and the like, preferably chloride.

The numbering system used throughout the specification is shown in thering system which is illustrated below. Ring systems of this type areusually named in the chemical literature as a6,11-substituted-6,11-dihydrobenzo[b]quinolizinium ##STR17## noliziniumor a 6,11-dihydro-6,11-substituted acridizinium. It should be noted,however, that in some of the earlier chemical literature references (seereferences cited in Information Disclosure Statement) ring systems ofthis type were numbered as shown below, and were named as a9,10-substituted-9,10-dihydro-4a-azoniaanthracene, or a9,10-dihydro-4a-azonia-9,10-substituted ##STR18## anthracene. Throughoutthis specification, however, we will use the former numbering system,and we will name the compounds as6,11-substituted-6,11-dihydrobenzo[b]quinolizinium salts.

The synthesis of the compounds of the invention may be outlined as shownin Scheme A:

Scheme A ##STR19##

A suitably substituted benzo[b]quinolizinium salt of Formula I can betreated with an excess of an appropriate cyclic diene or olefin of theFormula III, in a suitable solvent, e.g. acetonitrile, sulfolane,nitromethane, water, or alcoholic solvents, e.g. methanol, or mixturesof said solvents, at a temperature in the range of about roomtemperature up to the boiling point of the solvent or solvent mixtureused to produce the 6,11-substituted-6,11-dihydrobenzo[b]quinoliziniumsalts of Formula I where A is cycloalkenyl, tetrahydrofuranyl,cycloalkyl, or cycloalkenyl substituted at any available carbon atomthereof by lower-alkylidene. The corresponding compounds of the FormulaI wherein A is a phenyl ring can be prepared by procedures which areknown in the art of chemistry, for example, treating an appropriatelysubstituted benzo[b]quinolizinium salt of Formula II in a suitablesolvent, e.g. acetonitrile, concurrently with an excess of isoamylnitrite and anthranilic acid (forms benzyne in situ) in the samesolvent, followed by the addition of ether to precipitate the compoundsof Formula I wherein A is phenyl (see, for example, Fields et al., J.Org. Chem. 1971, 36(20), 2995-3001).

If desired, the compounds of Formula I can be converted into othercompounds of Formula I which possess various different anions (X⁻) by a)treating a solution of a compound of the Formula I in water with atleast one molar equivalent of the alkali metal salt of an organic acidanion or an inorganic acid anion, M⁺ X⁻, wherein the acid of the saltused is a stronger acid than the corresponding acid of the initial acidanion (X⁻), and wherein M⁺ is an alkali metal, e.g. lithium, sodium orpotassium; b) passing a compound of the Formula I wherein X⁻ is otherthan Cl⁻ through a Dowex® 1×2-200 ion-exchange resin (Dowex®-1-chloride)column to produce compounds of the Formula I wherein X⁻ is Cl⁻ ; or c)by passing a compound of the Formula I through a suitable ion-exchangeresin column (prepared, for example, by treating Dowex® 1X2-200ion-exchange resin with a suitable organic acid or inorganic acid) toprovide various compounds of Formula I wherein X⁻ is other than Cl⁻,ClO₄ ⁻ or PF₆ ⁻.

It will be appreciated that the compounds of the Formula I can possessone or more asymetric carbon atoms and are thus capable of existing in anumber of stereoisomeric forms, e.g. enantiomers, diastereomers, andgeometric isomers. Unless otherwise specified herein, the, invention isintended to extend to each of these stereoisomeric forms, and tomixtures thereof, including the racemates. In some cases there may beadvantages, e.g. greater potency, to using a particular enantiomer whencompared to the other enantiomer or the racemate in the treatment orprevention of neurodegenerative disorders or neurotoxic injuries, andsuch advantages can be readily determined by those skilled in the act.The different stereoisomeric forms may be separated one from the otherby the methods described hereinbelow:

The diastereomers/geometric isomers can be separated by conventionalprocedures which are well known in the art of chemistry such aschromatography, fractional crystallization and the like. The separationof enantiomers can be accomplished by a) chiral chromatography, or b)treating a racemic mixture of a compound of Formula I with the potassiumsalt of (+)-dibenzoyl-D-tartaric acid (K⁺ [(+)-DBT]) to afford acompound of Formula I as the ⁻ [(+)-DBT] salt; fractionalcrystallization of the ⁻ [(+)-DBT] salt to afford a single diastereomerof the ⁻ [(+)-DBT] salt, and then conversion of the single diastereomerof the ⁻ [(+)-DBT] salt into various other non-chiral anions (X⁻) byfollowing the procedures described hereinabove for the conversion ofcompounds of the Formula I into other compounds of the Formula I withvarious different anions (X⁻), to produce the compounds of the Formula Ias a single enantiomer; or c) treating a racemic mixture of a compoundof Formula I with the potassium salt of (-)-dibenzoyl-L-tartaric acid(K⁻ [(-)-DBT]) to afford a compound of Formula I as the ⁻ [(-)-DBT] saltand then proceeding as described hereinabove in part b to afford thecompounds of Formula I as the other enantiomer.

The suitably substituted benzo[b]quinolizinium salts of the Formula II,which are required for the synthesis of the compounds of the Formula I,are either known and can thus be prepared by procedures which are knownin the art of chemistry (see for example, Bradsher and Parham, J. Org.Chem., 1963, 28, 83-85; Bradsher and Jones, J. Am. Chem. Soc., 1957, 79,6033-34; Bradsher et al., J. Het. Chem. 1964, 1, 30-33; and Bradsher andParham, J. Het. Chem. 1964, 1, 121-124); or if they are novel, they canbe prepared by the procedures described in the an or those,describedhereinbelow and illustrated in Schemes B and C. In Scheme B, at leastone molar equivalent of an appropriately substituted benzyl halide (IV),wherein Z is a halogen, preferably chlorine, bromine, or iodine, istreated with one mole of an appropriately substituted

Scheme B ##STR20## stituted 2-(1,3-dioxolan-2-yl)pyridine (V), in thepresence of a solvent, e.g. sulfolane, or acetone, at a temperature inthe range of about room temperature up to the boiling point of thesolvent used, to produce the pyridinium salt (VI). The pyridinium salt(VI) can then be treated with an excess of an acid, e.g. polyphosphoricacid, 48% hydrobromic acid, or a mixture of polyphosphoric acid andmethanesulfonic acid at a temperature in the range of about 40° C. up tothe boiling point of the acid, or acid mixture used, to produce thecompounds of the Formula VII (Formula II wherein Z⁻ ═X⁻ ═halogen). Thecompounds of the Formula VII can then be converted into compounds of theFormula II which possess various anion groups, X⁻, by (a) treating acompound of the Formula VII, either as a solution in water, or neat,with or adding it to an aqueous solution containing at least one molarequivalent of the alkali metal salt of an organic acid anion or aninorganic acid anion, M⁺ X⁻, wherein the acid of the salt used is astronger acid than the corresponding acid of the initial acid anion, andwherein M⁺ is an alkali metal, preferably potassium, lithium, or sodium,and X⁻ is as defined hereinabove; at a temperature in the range of aboutroom temperature up to the boiling point of the aqueous solution, or (b)adding the alkali metal salt, M⁺ X⁻, as a solid, to, or treating it witha solution of the compound of Formula VII in water, at a temperature inthe range of about room temperature up to the boiling point of theaqueous solution.

Alternatively, the benzo[b]quinolizinium salts of Formula II can beprepared as shown in Scheme C. A suitably substituted benzyl alcohol(VIII) is treated with at least two molar equivalents of a lower-alkylalkali metal, preferably n-BuLi, optionally in the presence of at leastone mole of a second base, e.g. tetramethylethylenediamine, followed byaddition of an excess of a suitable pyridine derivative (IX), in anorganic solvent, such as ether; at room temperature or below, preferablyat a temperature in the range of about room temperature to about -30°C., to afford diol X. The diol X can then be treated

Scheme C ##STR21## with a) an excess of an acid, e.g. 45% hydrobromicacid in acetic acid, at a temperature in the range of room temperatureup to the boiling point of the acid used, or b) an excess oftrifluoromethanesulfonic anhydride ((TF)₂ O), in a suitable solvent, atabout room temperature or above, or c) at least one molar equivalent ofa phosphorous oxyhalide, preferably phosphorous oxychloride, at aboutroom temperature or above, to produce the compounds of the Formula II,which can in turn be converted into other benzo[b]quinolizinium salts ofthe Formula II which possess various different anion groups, X⁻, byfollowing the procedures described hereinabove. It will be noted thatthe method described hereinabove in Scheme C is the preferred methodwhen it is desired to prepare compounds of the Formula II which containsubstituents in the 6-, 10-, and/or 11-positions.

The appropriately substituted cyclic diene or olefin (III), the alkalimetal salts of an organic acid anion or an inorganic acid anion (M⁺ X⁻),benzyl halide (IV), 2-(1,3-dioxolan-2-yl)pyridine (V), benzyl alcohol(VIII) and pyridine derivative (IX) are commercially available, or theycan be prepared by procedures well known in the art, or by theprocedures described hereinbelow.

The compounds of Formula I are quinolizinium salts in which it ispreferred that the salts are pharmaceutically acceptable salts, that is,salts whose anions (X⁻) are relatively innocuous to the animal organismin pharmaceutical doses of the salts, so that the beneficial propertiesinherent in the compounds of the Formula I are not vitiated by sideeffects ascribable to the anions. In practicing the present invention itis convenient to use the anions (X⁻) of organic acids such asmethanesulfonic acid and toluenesulfonic acid, or the anions ofinorganic acids such as hydrobromic acid and hydrochloric acid. However,other appropriate pharmaceutically acceptable salts within the scope ofthe invention are those derived from the anions (X⁻) of other organicacids, organic diacids, or inorganic acids.

The structures of the compounds of the invention were established by themode of synthesis, and by one or more of elemental analysis, andinfrared, nuclear magnetic resonance and mass spectroscopy. The courseof the reactions and the identity and homogeneity of the products wereassessed by one or more of thin layer chromatography (TLC), highpressure liquid chromatography (HPLC), or gas-liquid chromatography(GLC).

The following examples will further illustrate the invention without,however, limiting it thereto. All melting points (m.p.) are in degreescentigrade (° C.) and are uncorrected.

Example 1

To a mixture of benzo[b]quinolizinium bromide (10 g, 0.04 mol) (Bradsherand Parham, J. Org. Chem. 1963, 28, 83-85, Example VIIa) in 100 mL ofacetonitrile/methanol (3:1) was added 3.55 g (0.044 mol) of1,3-cyclohexadiene in 5 mL of acetonitrile/methanol (3:1) and theresulting solution was stirred at room temperature for 3 hours. Thesolvent was removed in vacuo and the residue was recrystallized fromethyl acetate/methylene chloride (3×) to afford 9.3 g (67%) of6,11[3',4']-cyclohexenyl-6,11-dihydrobenzo[b]quinolizinium bromide(Formula I: R¹ ═R² ═H; A═[3',4']-cyclohexenyl; X⁻ ═--Br⁻), as anoff-white solid, m.p. 285°-290° C.

Example 2

A solution containing 11-methyl-benzo[b]quinolizinium perchlorate (1.0g, 3.4 mmol) (Bradsher and Parham, J. Org. Chem., 1963, 28, 83-85,Example VIII) and cyclopentadiene (2 mL, 23.4 mmol) in acetonitrile (40mL) was stirred at room temperature for 2 hours. The solvent was removedin vacuo and the residue was triturated with ethyl acetate. The solidproduct was filtered to afford 1.2 g (97%) of11-methyl-6,11[3',4']cyclopentenyl-6,11-dihydrobenzo[b]quinoliziniumperchlorate.

Example 3

A solution of 8-methoxybenzo[b]quinolizinium perchlorate (3.2 g, 10.3mmol) (Bradsher and Jones, J. Am. Chem. Soc, 1957, 79, 6033-34) inacetonitrile (100 mL) and methanol (35 mL) was cooled to 0° C. undernitrogen and cyclopentadiene (3.9 g, 59 mmol) was added. The mixture wasstirred at room temperature overnight, followed by refluxing thereaction mixture for an additional 4 hours. The solvent was removed invacuo and the residue was triturated with methanol, filtered, and theyellow solid thus obtained was washed with ether to afford 1.8 g (46%)of 8-methoxy-6,11[3',4']cyclopentenyl-6,11-dihydrobenzo[b]quinoliziniumperchlorate (Formula I: R² ═8-OCH₃ ; R¹ ═H; A═[3',4']-cyclopentenyl; X⁻═ClO₄ ⁻).

Example 4

A mixture of 2-(1,3-dioxolan-2-yl)pyridine (15.1 g, 0.1 mol) and4-bromobenzyl-bromide (25.0 g, 0.1 mol) in tetramethylene sulfone (25mL) was refluxed for 2 hours and allowed to stand for 16 hours. Thereaction mixture was diluted with ethyl acetate (500 mL) and the solidproduct thus obtained was isolated by filtration to yield 37 g (92%) of1-(4-bromobenzyl)-2-(1,3-dioxolan-2-yl)pyridinium bromide (Formula VI:R² ═4-Br; R¹ ═H; Z⁻ ═Br⁻) as a white solid.

(b)

A mixture of 1-(4-bromobenzyl)-2-(1,3-dioxolan-2-yl)pyridinium bromide(37 g, 0.092 mol) in 48% HBr (300 mL) was refluxed with stirring for 24hours. The reaction mixture was concentrated in vacuo and cold water(200 mL) was added to the residue. A yellow solid precipitated, whichwas isolated by filtration to yield 7.7 g (25%) of9-bromobenzo[b]quinolizinium bromide (Formula VII: R² ═9-Br; R¹ ═H; Z⁻═Br⁻).

(c)

To a mixture of 9-bromobenzo[b]quinolizinium bromide (7.7 g (0.0227 mol)in acetonitrile (75 mL) and nitromethane (75 mL) was added with stirringa solution of methanol (30 mL) and cyclopentadiene (10 mL). The mixturewas stirred for 7 hours and allowed to stand for 16 hours. The solventwas removed in vacuo and the residue was triturated with acetonitrileand the solid product thus obtained was isolated by filtration. Theproduct was recrystallized from ethanol to yield 7.2 g (78%) of9-bromo-6,11[3',4']cyclopentenyl-6,11-dihydrobenzo[b]quinoliziniumbromide (Formula I: R¹ ═H; R² ═9-Br; A═[3',4']cyclopentenyl; X⁻ ═Br⁻),as a white solid, m.p. 277°-9° C. (dec).

Example 5 (a)

A mixture of 4-fluorobenzylbromide (17.5 g, 0.093 mol), sulfolane (25mL) and 2-(1,3,-dioxolan-2-yl)pyridine (14.0 g, 0.093 mol) was stirredat room temperature for 2 hours, and then allowed to stand for 72 hours.The reaction mixture was diluted with ethyl acetate (200 mL) and theprecipate thus obtained was collected by filtration and washed withether to afford 31.08 g (98%) of1-(4-fluorobenzyl)-2-(1,3,-dioxolan-2-yl)pyridinium bromide (Formula VI:R² ═4-F; R¹ ═H; Z⁻ ═Br⁻).

(b)

1-(4-Fluorobenzyl)-2-(1,3-dioxolan-2-yl)pyridinium bromide (31 g, 0.091mol) was added to a mixture of polyphosphoric acid (350 g) andmethanesulfonic acid (100 mL) at 40° C. and the resulting: mixture washeated at 105° C. for 2 hours. The mixture was poured onto ice and thesolution was treated with charcoal. The mixture was added to an excessof sodium perchlorate and the solution was chilled and allowed to standfor 16 hours. A precipitate formed, which was collected by filtration toafford 15.9 g (59%) of 9-fluorobenzo-[b]quinolizinium perchlorate(Formula II: R² ═9-F; R¹ ═H; X⁻ ═ClO₄ ⁻), as a yellow solid, m.p.168°-173° C.

(c)

To a mixture of 9-fluorobenzo[b]quinolizinium perchlorate (15.94 g,0.0535 mol) in 100 mL of acetonitrile was added with stirring 18 g (0.27mol) of cyclopentadiene. The reaction mixture was stirred at roomtemperature for 3 hours, then allowed to stand at room temperature for16 hours. The solvent was removed in vacuo and the residue wastriturated with ether. The ether was decanted, and the solid residue wasstirred with ethyl acetate. The solid was collected by filtration andrecrystallized from acetonitrile/ether to yield 14.73 g (75.5%) of9-fluoro-6,11[3',4']cyclopentenyl-6,11-dihydrobenzo-[b]quinoliziniumperchlorate (Formula I: R¹ ═H; R² ═9-F; A═[3',4']cyclopentenyl; X⁻ ═ClO₄³¹ ), as a white solid, (m.p. 204°-5° C.).

Example 6

To a suspension of 9-nitrobenzo[b]quinolizinium perchlorate (2.6 g, 8mmol) (Bradsher et al., J. Het. Chem. 1964, 1, 30-33) in acetonitrile(20 mL) was added cyclopentadiene (2.6 g, 0.039 mol). The mixture wasstirred until a homogeneous solution was obtained and the solution wasfiltered. The solvent was removed in vacuo and the residue thus obtainedwas recrystallized from acetonitrile to afford 1.3 g (42%) of9-nitro-6,11[3',4']cyclopentenyl-6,11-dihydrobenzo[b]quinoliziniumperchlorate (Formula I: R² ═9-NO₂ ; R¹ ═H; A═[3',4']cyclopentenyl; X⁻═ClO₄ ⁻), as a white powder, m.p. 235°-237° C. (dec.).

Example 7

A mixture of benzo[b]quinolizinium bromide (4.0 g, 15.4 mmol) (Bradsherand Parham, J. Org. Chem. 1963, 28, 83-85, Example VIIa), dihydropyran(40 mL) and tetramethylene sulfone (20 mL) was heated to reflux for 6hours, and then stirred at room temperature overnight. The mixture wasdiluted with ethyl acetate (40 mL) and the precipitate thus obtained wascollected by filtration to afford 3.5 g (66%) of6,11[2',3']tetrahydropyranyl-6,11-dihydrobenzo[b]quinolizinium bromide,as a white solid.

Example 8

A mixture of benzo[b]quinolizinium bromide (2.6 g, 10 mmol) (Bradsherand Parham, J. Org. Chem. 1963, 28, 83-85, Example VIIa), and2,3-dihydrofuran (10 mL, 132 mmol) was heated to reflux andtetramethylene sulfone (10 mL) was added. The mixture was cooled to roomtemperature and stirred for 2 hours. The solvent was removed in vacuo,and the residue was stirred with ethyl acetate. A solid was collected byfiltration and dried to afford 0.36 g (10%) of6,11[2',3']tetrahydrofuranyl-6,11-dihydrobenzo[b]-quinolizinium bromide(Formula I: R¹ ═R² ═H; A═[2',3']tetrahydrofuranyl; X⁻ ═Br⁻), as a tansolid, m.p. 195°-200° C.

Example 9

To a solution of benzo[b]quinolizinium bromide (31 g, 0.12 mol)(Bradsher and Parham, J. Org. Chem. 1963, 28, 83-85, Example VIIa), inacetonitrile/methanol (3/1, 1000 mL) at room temperature was added inone portion freshly distilled cyclopentadiene (39.6 g, 0.6 mol). Themixture was stirred for 1.5 hours, and the solvent was removed in vacuo.The solid residue was slurried with ethyl acetate and the product wascollected by filtration and the residue was recrystallized frommethanol/tertbutylmethyl ether to afford 26.0 g (38%) of6,11[3',4']cyclopentenyl-6,11-dihydrobenzo[b]quinolizinium bromide(Formula I: R¹ ═R² ═H; A═[3',4']cyclopentenyl; X⁻ ═Br⁻).

Example 10 (a)

A mixture of 2-(1,3-dioxolan-2-yl)pyridine (19 g, 0.126 mol) andp-methoxybenzyl bromide (30 mL) in sulfolane (50 mL) was stirred at roomtemperature for 4.5 days. The reaction mixture was diluted with ethylacetate and cooled while stirring. The solvent was decanted to isolatean opaque oil. The oil was triturated with ethyl acetate (3×) and aglassy solid was filtered to yield 15.72 g (40.6%) of1-(4-methoxybenzyl-2-(1,3-dioxolan-2-yl)-pyridinium chloride (FormulaVI: R² ═4-OCH₃ ; R¹ ═H; Z--═Cl--).

(b)

A mixture of 1-(4-methoxybenzyl)-2-(1,3-dioxolan-2-yl)pyridiniumchloride (15 g, 0.049 mol) in 300 g of polyphosphoric acid was allowedto react at 120° C. for 3 hours. The reaction mixture was poured ontoice with stirring. The mixture was neutralized with dibasic sodiumphosphate and an aqueous solution of lithium perchlorate (1.1 equiv.)was added. The precipitated solid was filtered and dried to yield9-methoxybenzo[b]quinolizinium perchlorate (Formula II: R² ═OCH₃ ; R¹═H; X⁻ ═ClO₄ ⁻), as a yellow solid.

(c)

A mixture of 13 g (0.042 mol) of 9-methoxybenzo[b]quinoliziniumperchlorate and 30 mL (0.497 mol) of cyclopentadiene in 300 mL ofmethanol was stirred at room temperature for 24 hours. Additionalcyclopentadiene (10 mL) was added and the reaction mixture was stirredfor an additional 24 hours. The solvent was concentrated in vacuo andthe dark residue was triturated with hexane and ethyl acetaterespectively. The product was collected by filtration to afford crude9-methoxy-6,11[3',4']cyclopentenyl-6,11-dihydrobenzo[b]quinoliziniumperchlorate (Formula I: R² ═9═OCH₃ ; R¹ ═H; A═[3',4']cyclopentenyl X⁻═ClO⁻).

Example 11 (a)

To a solution of 3-methoxybenzylalcohol (50.0 g, 0.36 mol) in ether (1.1L) at -20° C. was added n-BuLi (76.0 mL, 0.756 mol) at such a rate thatthe internal temperature of the reaction was maintained at less than-10° C. When the addition of n-BuLi was complete, the mixture was warmedto room temperature and stirred for 2 hours. The mixture was cooled to0° C. and tetramethylethylene diamine (42.0 g, 0.36 mol) was added. Thereaction mixture was cooled to -30° C. and 2-pyridinecarboxaldehyde(58.0 g, 0.36 mol) was added over 5 minutes. The reaction was warmed to0° C. over a 30 minute period and was then quenched with water (500 mL).The mixture was chilled for 24 hours, and the product was collected byfiltration and washed with ether. The product was recrystallized fromethanol to afford 30.0 g (34%) ofα-[2-(hydroxymethyl)-6-methoxyphenyl]-2-pyridinemethanol (Formula X: R²═6-OCH₃ ; R¹ ═H). The mother liquor from the recrystallization step wasconcentrated, diluted with ether and refrigerated for 16 hours. A solidprecipitated, which was collected by filtration to afford an additional13.1 g of the desired product for a total of 43.1 g (49%).

(b)

A solution of α-[2-(hydroxymethyl)-6-methoxyphenyl]-2-pyridinemethanol(13.1 g, 0.053 mol) in 45% hydrobromic acid in acetic acid (75 mL) wasrefluxed for 20 hours. Additional 45% hydrobromic acid in acetic acid(25 mL) was added and refluxing was continued for another 4 hours. Thereaction mixture was cooled, poured into CH₂ Cl₂ (700 mL) and stirredfor several minutes. A solid precipitated, which was collected byfiltration to afford 9.0 g (59%) of 10-methoxybenzo[b]quinoliziniumbromide (Formula II: R² ═10-OCH₃ ; R³ ═R⁴ ═H; X⁻ ═Br⁻). The filtrate wasconcentrated in vacuo to afford 4.0 g (27%) of10-hydroxybenzo[b]quinolizinium bromide (Formula II: R² ═10-OH; R¹ ═H;X⁻ ═Br⁻).

(c)

10-Methoxybenzo[b]quinolizinium bromide (4.0 g, 0.014 mol) was added to150 mL of warm 10% potassium hexafluorophosphate in water. Afterstirring for 5 minutes, the precipitate which formed was collected byfiltration and washed with warm water, then hexane, to afford 3.0 g(61%) of 10-methoxybenzo[b]quinolizinium hexafluorophosphate (FormulaII: R² ═10-OCH₃ ; R¹ ═H; X⁻ ═PF₆ ⁻).

(d)

To a solution of 10-methoxybenzo[b]quinolizinium hexafluorophosphate(3.0 g, 8.4 mmol) in methanol/acetonitrile (3/1, 250 mL) was addedfreshly distilled cyclopentadiene (25 mL). The mixture was stirred atroom temperature for 2 hours, and then was allowed to stand for 16hours. The solvent was removed in vacuo and the residue was trituratedwith ethyl acetate and filtered to afford 2.6 g (74%) of10-methoxy-6,11[3',4']cyclopentenyl-6,11-dihydrobenzo[b]quinoliziniumhexafluorophosphate (Formula I: R² ═10-OCH₃ ; R¹ ═H;A═[3',4']cyclopentenyl; X⁻ ═PF₆ ⁻).

Example 12 (a)

A mixture of 2-(1,3-dioxolan-2-yl)pyridine (3.9 g, 0.026 mol),1-iodoethylbenzene (6.0 g, 0.026 mol) and acetone (50 mL) was stirred atroom temperature under nitrogen. The acetone was removed, and sulfolane(50 mL) and additional 1-iodoethylbenzene (0.5 equivalents) was addedand the mixture was stirred for 24 hours. The mixture was diluted withethyl acetate, and the precipitate which formed was collected byfiltration to afford 3.7 g (37%) of1-(1-phenylethyl)-2-(1,3-dioxolan-2-yl)pyridinium iodide (Formula VI: R²═H; R¹ ═CH₃ ; Z⁻ ═I⁻).

(b)

A mixture of 1-(1-phenylethyl)-2-(1,3-dioxolan-2-yl)pyridinium iodide(3.5 g, 9 mmol) and 48% hydrobromic acid (20 mL) was refluxed for 16hours. The solvent was removed in vacuo to afford 1.9 g (76%) of6-methylbenzo[b]quinolizinium bromide (Formula VII: R² ═H;R¹ ═CH₃ ; Z⁻═Br⁻).

(c)

A mixture of 6-methylbenzo[b]quinolizinium bromide (1.8 g, 7 mmol),cyclopentadiene (2.6 g, 0.039 mol) and methanol was stirred at roomtemperature for 48 hours. The solvent was removed in vacuo and theresidue was dissolved in water, washed with ether, treated with charcoaland filtered through celite. Sodium perchlorate (857 mg, 7 mmol) wasadded to the filtrate and the solution was cooled. A solid precipitated,which was collected by filtration and washed with ether to afford 365 mg(15%) of6-methyl-6,11[3',4']cyclopentenyl-6,11-dihydrobenzo[b]quinoliziniumperchlorate, .1/2 H₂ O (Formula I: R² ═H; R¹ ═CH₃ ;A═[3',4']cyclopentenyl; X⁻ ClO₄ ⁻), as a tan solid, m.p. 239°-241° C.(dec.).

Example 13

A mixture of benzo[b]quinolizinium bromide (5.0 g, 0.02 mol), (Bradsherand Parham, J. Org. Chem. 1963, 28, 83-85, Example VIIa), methanol (3mL), water (40 mL) and cyclopentene (3.3 mL, 0.04 mL) was heated to 65°C. in a sealed tube for 2 hours. Additional methanol (5.0 mL) was addedand heating was continued at 65° C. for 8 hours. Additional methanol(3.0 mL) was again added and the mixture was heated at 65° C. for about17 hours. The solvent was removed in vacuo and the residue was purifiedby column chromatography on silica eluting with ethyl acetate/PAW (1/1,wherein PAW is pyridine/acetic acid/water (55/20/25) to afford twofractions, each of which contains a single geometric isomer, as well asa third fraction which contains 4.0 g of a mixture of both isomers. Eachof the isomers was individually treated with water (20 mL), followed bysodium perchlorate to afford 0.2 g (2.8%) of6,11[1',2']cyclopentyl-6,11-dihydrobenzo[b]quinolizinium perchlorate.1/2hydrate (Example 13(a)) (Formula I: R¹ ═R² ═H; A═[1',2']cyclopentyl; X⁻═ClO₄ ⁻), as one geometric isomer, and 0.88 g (12%) of6,11[1',2']cyclopentyl-6,11-dihydrobenzo[b]quinolizinium perchlorate.1/2hydrate (Example 13(b) (Formula I: R¹ ═R² ═H; A═[1',2']cyclopentyl; X⁻═ClO₄ ⁻), as the other geometric isomer. The first isomer was isolatedas a white solid, m.p. 198°-201° C. and the second isomer was isolatedas a tan solid, m.p. 217°-222° C.

Example 14 (a)

Benzo[b]quinolizium bromide (508.5 g, 1.95 mol) was dissolved indistilled water (5L) with heating on a steam bath and potassiumhexafluorophosphate (367.2 g, 1.95 mol) in water (1.1 L) was poured intothis solution in portions. The mixture was stirred at ambienttemperature for 3 hours, then in an ice-bath for 1 hour. The precipitatewhich formed was collected by filtration, washed with water and dried at60° C. in vacuo to afford 601 g (94.8%) of benzo[b]quinoliziniumhexafluorophosphate (Formula II: R¹ ═R² ═H; X⁻ ═PF₆ ⁻).

(b)

A solution of 5 g (0.0163 mol) of benzo[b]quinoliziniumhexafluorophosphate and 5 g (0.047 mol) of 6,6-dimethylfulvene innitromethane (60 mL) was allowed to reflux for 1 hour and cooled. Abrown solid product (700 mg) formed, which was isolated by filtrationand purified by column chromatography on silica eluting withmethanol/methylene chloride (1:10) and ethyl acetate. The productisolated was passed through Dowex(Cl⁻ ; 1×2-200; 50 g resin, 1000 mLwater). The purified product in water was treated with NaClO₄ and theprecipitated perchlorate was filtered and dried to yield 254 mg (4%) of6,11-[5'-isopropylidene-[3',4']cyclopentenyl]-6,11-dihydrobenzo[b]quinoliziniumperchlorate (Formula I: R¹ ═R² ═H;A═[5'-isopropylidene-[3',4']cyclopentenyl]; X⁻ ClO₄ ⁻).

Following procedures similar to those described hereinabove, or byfollowing procedures which are known in the art, the following knowncompounds (Examples 15a-15d) were prepared and, unexpectedly, they werefound to bind to the PCP receptor and are thus useful in the treatmentor prevention of neurodegenerative disorders or neurotoxic injuries.

Example 15 (a)

6,11-[3',4']cyclopentenyl-6,11-dihydrobenzo[b]quinolizinium bromide(Formula I: R¹ ═R² ═H; A═[3',4']cyclopentenyl; X⁻ ═Br⁻).

(b)

7-Nitro-6,11-benzeno-6,11-dihydrobenzo[b]quinolizinium perchlorate(Formula I: R¹ ═H; R² ═7-NO₂ ; A═phenyl; X⁻ ClO₄ ⁻).

(c)

7-Hydroxy-10-tert-butyl-6,11-benzeno-6,11-dihydrobenzo[b]quinoliziniumperchlorate (Formula I: R¹ ═H; R² ═7-OH,10-C(CH₃)₃ ; A═phenyl; X⁻ ClO₄⁻).

(d)

7-Methyl-6,11-benzeno-6,11-dihydrobenzo[b]quinolizinium perchlorate(Formula I: R¹ ═H; R² ═7-CH₃ ; A═phenyl; X⁻ ClO₄ ⁻).

BIOLOGICAL TEST RESULTS

Representative examples of the compounds of the invention have beenfound to possess valuable pharmacological properties. In particular,they have been found to bind to the PCP receptor and are thusnon-competitive blockers (antagonists) of the effects which excitatoryamino acids, such as glutamate, have upon the NMDA receptor. Thecompounds of the invention are thus useful in the treatment orprevention of neurodegenerative disorders such as Huntington's disease,Alzheimer's disease, amyotrophic lateral sclerosis, Down's Syndrome,senile dementia, glutaric acidaemia type I multi-infarct dementia,Parkinson's disease, vital encephalopathies (which include, but are notlimited thereto, dementia associated with HIV infections) and neuronaldamage associated with uncontrolled seizures, as well as in thetreatment or prevention of neurotoxic injuries associated with ischemic,hypoxic; or hypoglycemic conditions. Representative examples of suchischemic, hypoxic, or hypoglycemic conditions include strokes orcerebrovascular accidents, carbon monoxide poisoning, hyperinsulinemia,cardiac arrest, drownings, suffocation, spinal or head trauma, coronaryartery bypass graft, neonatal anoxic trauma, and perinatal asphyxia.

The compounds of the invention are particularly useful in the treatmentor prevention of neurotoxic injuries associated with ischemic, hypoxic;or hypoglycemic conditions, and especially ischemic, hypoxic, orhypoglycemic conditions which are associated with stroke.

The pharmacological properties of representative examples of thecompounds of the invention was demonstrated by conventional in vitrobiological test procedures such as the following:

[³ H]TCP Radioreceptor Assay (internal screen)

[³ H]TCP binding to PCP recognition sites was performed as described byVignon et al. Brain Research 1983, 280, 194-197. Male Sprague-Dawleyrats were sacrificed by decapitation, and whole brains were homogenizedin 10 volumes (wt/vol) of cold Tris-HCl buffer (50 mM, pH 7.7) using aBrinkmann Polytron (setting 6, 30 sec). The homogenate was centrifugedat 40,000×g for 10 min at 4° C. The supernatant was decanted, and thehomogenization and centrifugation steps were repeated twice as describedabove. Following this, the pellet was resuspended in Tris-HCl (5 mM, pH7.7) at a tissue concentration of 0.5-0.75 g/ml, and one ml aliquotswere frozen at -70° C. until use. The binding characteristics for PCPrecognition sites were not altered by the freezing of membranesuspensions.

On the day of the assay, membrane aliquots were thawed, resuspended infresh 5 mM Tris-HCl buffer at a tissue concentration of 1 mg/ml, andstored on ice until use. Each assay tube contained 100 μl of [³ H]TCP ata final concentration of approximately 1 nM, 100 μl of variousconcentrations of the compounds of interest, 500 μl of the tissuesuspension and 300 μl of buffer to a final assay volume of 1 ml and afinal protein concentration of 0.5 mg/tube. Non-specific binding wasdefined by addition of a final concentration of 100 μM PCP to blanktubes. All tubes were incubated at room temperature for 25 min beforetermination of the reaction by rapid filtration over Whatman GF/B glassfiber filters that had been presoaked in a solution of 0.5%polyethylenimine for at least 1 hr prior to use. Filters were washedwith three 4 ml volumes of cold Tris buffer. Following addition ofscintillation cocktail, the amount of bound radioactivity was determinedby liquid scintillation spectrometry using a Beckman LS 5000TA liquidscintillation counter with an efficiency for tritium of approximately55%. Inhibition constants (K_(i) values) were calculated using theEBDA/LIGAND program (McPherson, J. Pharmacol. Meth. 1985, 14, 213-228),purchased from Elsevier/Biosoft, Inc. Results are reported as K_(i)values which are expressed as the mean of at least two separatedeterminations; or as a percent (%) inhibition of binding at 10 μM.

Representative compounds of the invention were also tested in anexternal [³ H]TCP radioreceptor assay using the following protocol:

[³ H]TCP Radioreceptor Assay (external screen)

A procedure similar to that described above, for the [³ H]TCPradioreceptor assay (internal screen) was utilized except that the wholerat forebrain membranes were incubated at 25° C. for 60 minutes ratherthan at room temperature for 25 minutes, before termination of thereaction. The results are reported as a percent (%) inhibition ofbinding at 10 μM.

Antagonism of NMDA-induced Neurotoxicity in Cultured Neurons Preparationof Cultured Cortical Neurons

Pregnant, Swiss-Webster mice were obtained from Taconic Farms(Germantown, N.Y.) and sacrificed 16 days post conception. Fetuses wereremoved and placed in a sterile dish containing Hank's balanced saltsolution (HBSS), pH 7.4. Brain cortices were dissected, meninges wereremoved, the tissue was minced and placed into a solution of HBSScontaining 0.25% (w/v) trypsin at 37° C. for 15 minutes. Tissue was thentriturated with a sterile pasteur pipet, diluted with minimal essentialmedia (Gibco 330-1430), pH 7.4, supplemented with 10% horse serum, 10%fetal calf serum, 2 mM 1-glutamine, 21 mM d-glucose, 2.2 g/L sodiumbicarbonate, 1000 U/ml penicillin, and 1,000 μg/ml streptomycin. Cellswere plated onto Falcon primaria 96 well plates at a final density of50,000 cells/well and incubated at 37° C. in the presence of 5% (v/v)carbon dioxide. After 5 days, plating media was replaced withmaintenance media containing minimal essential media (Gibco 330-1430),pH 7.4, supplemented with 10% horse serum, 10% 1-glutamine, 21 mMd-glucose, 2.2 g/l sodium bicarbonate, 1,000 U/ml penicillin, 1,000μg/ml streptomycin, and 10 μM cytosine arabinoside. On days 7 and 10,media was replaced with maintenance media as above lacking the cytosinearabinoside. Experiments were conducted on day 13.

Neuroprotection Assessment

Day 13 cultured cortical neurons were washed twice with minimalessential media, pH 7.4 and then exposed for 30 minutes to 500 μMN-methyl-D-aspartic acid (NMDA) with or without varying concentrationsof test agents. Dizocilpine (MK-801) at a final concentration of 10 μMMK-801 was routinely included as a positive control. MK-801 and testagents were prepared in minimal essential media supplemented with 21 mMd-glucose and 2.2 g/L sodium bicarbonate (MEM). After 30 minutes, mediawas replaced with MEM alone. Exposure of neurons to test agents waslimited to the NMDA treatment period. Twenty-four hours after removal ofNMDA, an aliquot of media from each well was removed for assessment ofcell injury by determining lactate dehydrogenase (LDH) activity by themethod of Wroblewski and LaDue Proc. Soc. Exp. Biol. Med. 1955, 90,210-213. The results are expressed as an IC₅₀ (in nM) value(concentration causing 50% inhibition) for the antagonism ofNMDA-induced neurotoxicity.

Table 1 summarizes the results obtained from the testing ofrepresentative compounds of the invention in the [³ H]TCP radioreceptorassay (internal screen and external screen) as well as in the antagonismof NMDA-induced neurotoxicity in cultured neurons.

                  TABLE 1                                                         ______________________________________                                               [.sup.3 H]TCP                                                                              [.sup.3 H]TCP                                                    (internal screen)                                                                          (external   Antagonism of                                        K.sub.i (nM) or                                                                            screen) Per-                                                                              NMDA-induced                                  Example                                                                              Percent Inhibition                                                                         cent Inhibition                                                                           neurotoxicity                                 Number @10 μM    (%) @10 μM                                                                             (IC.sub.50 in nM)                             ______________________________________                                         1     245          --          --                                             4(c)  1626         --          --                                             5(c)  806          --          --                                             8     8494         --          --                                            12(c)  93.4         --          --                                            13(a)  1565         --          --                                            13(b)  366          --          8400                                          14(b)  367          --          --                                            15(a)  464          92%         --                                            15(b)  37%           9%         --                                            15(c)  10%          24%         --                                            15(d)  52%          11%         --                                            ______________________________________                                    

The compounds of the invention can be prepared for pharmaceutical use byconventional pharmaceutical procedures that are well known in the art;that is, by formulating a pharmaceutical composition which comprisescompounds of the invention or their pharmaceutically acceptable saltstogether with one or more physiologically acceptable carriers,adjuvants, diluents or vehicles, for oral administration in solid orliquid form, parenteral administration, topical administration oraerosol inhalation administration, and the like.

Solid compositions for oral administration include compressed tablets,pills, powders and granules. In such solid compositions, the activecompound is admixed with at least one inert diluent such as starch,calcium carbonate, sucrose or lactose. These compositions may alsocontain additional substances other than inert diluents, e.g.,lubricating agents, such as magnesium stearate, talc and the like.

Liquid compositions for oral administration include pharmaceuticallyacceptable emulsions, solutions, suspensions, syrups and elixirscontaining inert diluents commonly used in the art, such as water andliquid paraffin. Besides inert diluents such compositions may alsocontain adjuvants, such as wetting and suspending agents, andsweetening, flavoring, perfuming and preserving agents. According to theinvention, the compounds for oral administration also include capsulesof absorbable material, such as gelatin, containing said activecomponent with or without the addition of diluents or excipients.

Preparations according to the invention for parenteral administrationinclude sterile aqueous, aqueous-organic, and organic solutions,suspensions and emulsions. Examples of organic solvents or suspendingmedia are propylene glycol, polyethylene glycol, vegetable oils such asolive oil and injectable organic esters such as ethyl oleate. Thesecompositions can also contain adjuvants such as stabilizing, preserving,wetting, emulsifying and dispersing agents.

Preparations according to the invention for topical administration oraerosol inhalation administration include dissolving or suspending acompound of the invention in a pharmaceutically acceptable vehicle suchas water, aqueous alcohol, glycol, oil solution or oil-water emulsion,and the like.

If desired, the compounds of the invention can further be incorporatedinto slow release or targeted delivery systems such as polymer matrices,liposomes, and microspheres.

The percentage of active component in such compositions may be varied sothat a suitable dosage is obtained. The dosage administered to aparticular patient is variable depending upon the clinician's judgmentusing as criteria: The route of administration, the duration oftreatment, the size and physical condition of the patient, the potencyof the active component and the patient's response thereto. An effectivedosage amount of the active component can thus readily be determined bythe clinician after a consideration of all criteria and using his bestjudgment on the patient's behalf.

We claim:
 1. A compound of the formula: ##STR22## wherein: R¹ ishydrogen, or lower-alkyl;R² is hydrogen, or from one to four, the sameor different, halogen substituents in any of the 7-,8-,9- or10-positions; A is cycloalkenyl, or said ring substituted at anyavailable carbon atom thereof by lower-alkylidene; and X⁻ is an anion;ora hydrate thereof; or a stereoisomer thereof; with the proviso that whenR¹ and R² are hydrogen and X⁻ is Br⁻, or ClO₄ ⁻, A cannot be[3',4']cyclopentenyl.
 2. A compound according to claim 1 wherein R¹ ishydrogen, or methyl; and R² is hydrogen or one halogen substituent inany of the 7-,8-,9- or 10-positions.
 3. A compound according to claim 2wherein R² is hydrogen or a bromine or fluorine substituent in any ofthe 7-,8-,9- or 10-positions; and A is a cyclopentenyl, or cyclohexenylring, or said cyclopentenyl ring substituted on any available carbonatom thereof by lower-alkylidene.
 4. A compound according to claim 3wherein R² is hydrogen, 9-Br or 9-F; and A is a [3',4']cyclohexenyl,[3',4']cyclopentenyl, or [5'-isopropylidene[3',4']cyclopentenyl] ring.5. 6-methyl-6,11-[3',4']cyclopentenyl-6,11-dihydrobenzo[b]quinoliziniumperchlorate according to claim
 4. 6. A pharmaceutical composition whichcomprises a compound of the formula: ##STR23## wherein: R¹ is hydrogen,or lower-alkyl;R² is hydrogen, or from one to four, the same ordifferent, substituents in any of the 7-,8-,9- or 10-positions selectedfrom the group consisting of halogen, nitro, lower-alkoxy, hydroxy, andlower-alkyl; A is a member selected from the group consisting ofcycloalkenyl, tetrahydrofuranyl, cycloalkyl, cycloalkenyl substituted atany available carbon atom thereof by lower-alkylidene; and phenyl; andX⁻ is an anion;or a hydrate thereof; or a stereoisomer thereof; togetherwith a pharmaceutically acceptable carrier, adjuvant, diluent, orvehicle; with the following provisos a) when R¹ is hydrogen, R² is9-nitro and X⁻ is ClO₄ ⁻, A cannot be [3',4']cyclopentenyl; b) when R¹is hydrogen, R² is 7,10-dihydroxy and X⁻ is Br⁻, A cannot be[3',4']cyclopentenyl; (c) when R¹ and R² are hydrogen and X⁻ is ClO₄ ⁻,A cannot be phenyl; and (d) when R¹ is hydrogen, R² is 9-methyl and X⁻is ClO₄ ⁻, A cannot be phenyl.
 7. A pharmaceutical composition accordingto claim 6 wherein:R¹ is hydrogen, or methyl; R² is hydrogen, or fromone to two, the same or different, substituents in any of the 7-,8-,9-or 10-positions selected from the group consisting of halogen, nitro,hydroxy, and lower-alkyl; and A is a member selected from the groupconsisting of cyclohexenyl, cyclopentenyl, cyclopentenyl substituted atany available carbon atom thereof by lower-alkylidene;tetrahydrofuranyl, cycloalkyl and phenyl.
 8. A pharmaceuticalcomposition according to claim 7 wherein:R² is hydrogen, or from one totwo, the same or different, substituents in any of the 7-,8-,9- or10-positions selected from the group consisting of bromine, fluorine,nitro, hydroxy, methyl and tert-butyl; and A is a member selected fromthe group consisting of [3',4']cyclohexenyl, [2',3']tetrahydrofuranyl,[3',4']cyclopentenyl, cyclopentyl,[5'-isopropylidene[3',4']cyclopentenyl] and phenyl.
 9. A pharmaceuticalcomposition which comprises a compound according to claim 1 togetherwith a pharmaceutically acceptable carrier, adjuvant, diluent, orvehicle.
 10. A pharmaceutical composition which comprises a compoundaccording to claim 3 together with a pharmaceutically acceptablecarrier, adjuvant, diluent, or vehicle.
 11. A pharmaceutical compositionwhich comprises a compound according to claim 4 together with apharmaceutically acceptable carrier, adjuvant, diluent, or vehicle. 12.A pharmaceutical composition which comprises a compound according toclaim 5 together with a pharmaceutically acceptable carrier, adjuvant,diluent, or vehicle.
 13. A method for the treatment of neurodegenerativedisorders or the treatment or prevention of a neurotoxic injuries whichcomprises administering to a patient in need of such treatment aneffective amount of a compound of the formula: ##STR24## wherein: R¹ ishydrogen, or lower-alkyl;R² is hydrogen, or from one to four, the sameor different, substituents in any of the 7-,8-,9- or 10-positionsselected from the group consisting of halogen, nitro, lower-alkoxy,hydroxy, and lower-alkyl; A is a member selected from the groupconsisting of cycloalkenyl, tetrahydrofuranyl, cycloalkyl, cycloalkenylsubstituted at any available carbon atom thereof by lower-alkylidene;and phenyl; and X⁻ is an anion;or a hydrate thereof; or a stereoisomerthereof; with the following provisos a) when R¹ is hydrogen, R² is9-nitro and X⁻ is ClO₄ ⁻, A cannot be [3',4']cyclopentenyl; b) when R¹is hydrogen, R² is 7,10-dihydroxy and X⁻ is Br⁻, A cannot be[3',4']cyclopentenyl; (c) when R¹ and R² are hydrogen and X⁻ is ClO₄ ⁻,A cannot be phenyl; and (d) when R¹ is hydrogen, R² is 9-methyl and X⁻is ClO₄ ⁻, A cannot be phenyl.
 14. A method according to claim 13wherein:R¹ is hydrogen, or methyl; R² is hydrogen, or from one to two,the same or different, substituents in any of the 7-,8-,9- or10-positions selected from the group consisting of halogen, nitro,hydroxy, and lower-alkyl; and A is a member selected from the groupconsisting of cyclohexenyl, cyclopentenyl, cyclopentenyl substituted atany available carbon atom thereof by lower-alkylidene;tetrahydrofuranyl, cycloalkyl and phenyl.
 15. A method according toclaim 14 wherein:R² is hydrogen, or from one to two, the same ordifferent, substituents in any of the 7-,8-,9- or 10-positions selectedfrom the group consisting of bromine, fluorine, nitro, hydroxy, methyland tert-butyl; and A is a member selected from the group consisting of[3',4']cyclohexenyl, [2',3']tetrahydropyranyl, [3',4']cyclopentenyl,cyclopentyl, [5'-isopropylidene[3',4']cyclopentenyl] and phenyl.
 16. Amethod for the treatment of neurodegenerative disorders or the treatmentor prevention of neurotoxic injuries which comprises administering to apatient in need of such treatment an effective amount of a compoundaccording to claim
 1. 17. A method for the treatment ofneurodegenerative disorders or the treatment or prevention of neurotoxicinjuries which comprises administering to a patient in need of suchtreatment an effective amount of a compound according to claim
 3. 18. Amethod for the treatment of neurodegenerative disorders or the treatmentor prevention of neurotoxic injuries which comprises administering to apatient in need of such treatment an effective amount of a compoundaccording to claim
 4. 19. A method for the treatment ofneurodegenerative disorders or the treatment or prevention of neurotoxicinjuries which comprises administering to a patient in need of suchtreatment an effective amount of a compound according to claim
 5. 20. Amethod according to claim 13 for the treatment of neurodegenerativedisorders.
 21. A method according to claim 13 for the treatment orprevention of neurotoxic injuries.
 22. A method according to claim 21wherein said neurotoxic injuries are associated with ischemic, hypoxic,or hypoglycemic conditions.
 23. A method according to claim 22 whereinsaid ischemic, hypoxic, or hypoglycemic conditions are associated withstroke.